By Brian Carnell

Tuesday, April 23, 2002

One of the claims made by anti-vaccination advocates is that thimerosal in vaccines contributes to autism. But as Quackwatch.Com recently noted in a summary of the claims over thimerosal, there is no evidence to back up that claim.

Thimerosal is a preservative that contains mercury. It has been used as a preservative in vaccines since the 1930s.

Many anti-vaccination advocates are convinced exposure to mercury in vaccines accounts for the perceived rise in the number of autistic children. But as Quackwatch notes, so far no study has found any sort of difference in autism incidence between children who were exposed to very little or no thimerosal and those who received the maximum cumulative exposure (which works out to something like 187.5 micrograms in the first six months of life).

One study did find a weak association with thimerosal exposure and attention deficit disorder, but another study found no association and the first study's results have yet to be duplicated.

And yet, according to Quackwatch, based on this lack of evidence some physicians are recommending chelation therapy for autistic children. Unlike thimerosal, there are known risks to chelation, which involves the intravenous infusion of disodium EDTA and other substances. As Quackwatch notes,

Other observers have reported cases of hypocalcemia leading to cardiac arrhythmias and tetany; kidney damage; decreased blood clotting ability with abnormal bleeding; thrombophlebitis and embolism; hypoglycemia and insulin shock; severe vasculitis and autoimmune related hemolytic anemia, dermatitis with pruritus and generalized eczema; and extensive clumping of platelets in the blood of some patients with atherosclerosis and other chronic diseases.

Chelation therapy appears to dramatically reduce the level of zinc in the body as well which can lead to a number of problem such as diminished immune function.

Source:

Misconceptions about Immunizations: Misconception #11, Thimerosal Causes Autism. QuackWatch.Com, April 20, 2002.

Chelation Therapy: Unproven Claims and Unsound Theories. Saul Green, Ph.D., September 14, 2000.

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